Effects of Ascochyta blight caused by Mycosphaerella pinodes on the translocation of carbohydrates and nitrogenous compounds from the leaf and hull to the seed of dried-pea

The effects of Ascochyta blight (caused by Mycosphaerella pinodes ) on changes in dry weight and in water, carbohydrate, nitrogen and free amino acid contents were studied in the leaf, the hull and the seeds on the second fructifer node of pea ( Pisum sativum ). Pea plants were grown in a glasshouse and inoculated with various concentrations of conidia at the beginning of seed filling, with uninoculated plants as controls. Disease induced a premature water loss of hulls and leaves, accelerated seed desiccation and reduced seed weight. Biochemical analyses revealed a decline in the carbohydrate content and a lower nitrogen remobilization in diseased leaves and hulls. Thus, Ascochyta blight alters carbohydrate metabolism, protein remobilization and free amino acid translocation from these organs. Disease also reduced carbohydrate and nitrogen content in seeds and, in case of high disease severity, the carbohydrate/nitrogen ratio in the seeds was also affected (seed protein concentration increased and starch concentration decreased).     

加工型辣椒品种对细菌性叶斑病的抗性鉴定

由黄褐假单胞Pseudomonas fulva侵染引起的辣椒细菌性叶斑病是近期在新疆北疆加工辣椒生产区发现的一种新病害。为评估辣椒品种对细菌性叶斑病的抗性水平,采用苗期人工接种结合田间调查,鉴定了生产中13个主栽辣椒品种对细菌性叶斑病的抗性。结果表明,供试材料对细菌性叶斑病均无免疫性,但不同辣椒品种对辣椒叶斑病抗性差异较大,‘改良佳线1号’和‘丰力红冠’为抗病品种;‘佳线4号’、‘新丰6号’、‘秦椒王’、‘陕早红’、‘宝丰2号’为耐病品种;‘红安6号’、‘朝天椒’为感病品种,高感品种为‘金塔’、‘铁皮椒’、‘红龙13’和‘超级韩国甜椒’。研究结果为辣椒的抗病育种和病害防治提供了基础。     

Discovery of Didymella fabae sp. nov., the teleomorph of Ascochyta fabae, on faba bean straw

The teleomorph of Ascochyta fabae has been recorded for the first time on overwintering bean straw of Viciafaba in Cambridge. Single ascospores gave rise to typical cultures of A. fabae, the conidia of which infected faba bean plants to give ascochyta blight. Comparison with similar fungi described from Vicia spp. indicated that this is an undescribed species. The name Didymella fabae Jellis & Punith. is introduced for this teleomorph and its significance in the epidemiology of the disease is discussed.     

Effects of Ascochyta blight (Mycosphaerella pinodes) on the photosynthesizing leaf area and the photosynthetic efficiency of the green leaf area of dried-pea (Pisum sativum)

The effects of Ascochyta blight (caused by Mycosphaerella pinodes ) on the net photosynthetic rate of glasshouse-grown dried pea were studied on foliar discs and whole plants in pots showing different disease intensities, assessed visually using a disease scale (scores 0 to 5) or by an estimation of the fraction of leaf area with necrosis using an image analyser. The photosynthetic rate of foliar discs was measured using a leaf disc electrode; for plants it was assessed by CO₂ exchange rate measurements in a closed chamber. A reduction in the net photosynthetic rate of diseased plants was correlated with an increase in disease score. A 53–56% reduction was found in foliar discs with a mean disease score of 3. On whole plants, mean scores of 3.5 and 4.0 were associated with reductions of 36% and 98% respectively. The disease also induced a decrease in the photosynthetic efficiency of the non-necrotic leaf area. The photosynthetic rate was zero when 30–40% of foliar area was necrotic on foliar discs and on whole plants. A function was derived from the foliar disc data that described the dependence of photosynthetic rate on the fraction of leaf area without necrosis. The model is discussed with reference to data obtained from entire plants and other pathosystems.     

水稻细菌性基腐病的侵染规律和病理解剖学研究

 水稻细菌性基腐病是近年来发现并日趋严重的水稻病害.经鉴定,病原菌的细菌学性状与菊欧氏杆菌玉米致病变种(Erwinia chrysanthemi PV.Zeal)相似。本文通过接种实验和扫描电镜观察,证明基腐病细菌可从叶片上的水孔、伤口、受伤的叶鞘和根系侵入,引起不同类型的症状,而以根系侵入为主.首次报导该病原菌侵入后主要在根、茎的气腔中作系统侵染.     

水稻叶鞘腐败病的研究——Ⅰ.病原菌的致病性及发病的影响因子

 本文阐述了水稻叶鞘腐败病病原菌Sarocladium oryzae,在水稻各生育期和植株不同部位的叶鞘上之致病性以及由此产生的各种症状。该病原菌不仅在水稻各生育期发生危害,还能侵害叶鞘、谷粒、叶片中脉等。水稻剑叶叶鞘受害,常呈现为典型叶鞘腐败病病斑以及"紫鞘"或"紫鞘黄叶"症状。病谷常引起秧苗发病。发病的最适温度为30℃、湿度为70%(RH)。但发病对温湿度要求并不甚严格。适当的氮、磷、钾配比和适量施用能提高植株的抗病性,氮肥过多或缺乏均会加剧病害的发生与危害。品种的抗病性有着明显差异,但与水稻类型无关。以病原菌分生孢子液对21个常见杂草和野生稻接种,其中属于禾本科的15个种可引起发病。经田间调查,该病原菌也在自然条件下侵染若干禾本科杂草。     

Clove-transmissibility of <Emphasis Type="Italic">Pseudomonas salomonii</Emphasis>, the causal agent of ‘Café au lait’ disease of garlic

Bacterial blight of garlic, caused by Pseudomonas salomonii, results in leaf and sheath necrosis and sometimes leads to soft rot and plant death. The epidemiology of this bacterial disease, known as ‘Café au lait’ disease, is poorly understood and no resistant cultivars are currently available. To develop control strategies for this disease, we investigated principal sources of inoculum. The pathogen was isolated from bulbs from plants with typical vegetative symptoms of bacterial blight. Subsequent development of typical foliar symptoms on plantlets originating from symptomatic bulbs demonstrated transmission of the pathogen in the planting material. In one of three field experiments the contamination rate of planting stock influenced the disease incidence in field-grown garlic. The importance of planting stock as a source of inoculum was demonstrated here and should be evaluated relative to other potential sources such as crop debris, soil or alternate hosts in order to develop successful control strategies.     

Effects of sowing date on severity of blight caused by <Emphasis Type="Italic">Ascochyta rabiei</Emphasis> and yield components of five chickpea cultivars grown under two climatic conditions in Tunisia

Five chickpea cultivars, Chitoui, Neyer, Kasseb, Beja 1 and Bouchra, were planted on three sowing dates at two Experimental Stations in Tunisia: Bou Salem in the north and the more southerly Mornag, where the climate is drier. Severity of blight, caused by Ascochyta rabiei, was measured on a 1–9 scale (defined) on vegetative parts and on pods as percent infected and percent infected that were empty. At both locations, disease was essentially absent on plants sown on the third dates but present on plants sown on the two earlier dates. At Bou Salem, disease severity was highest for the second sowing date whereas at Mornag it was highest for the first sowing date; but for each sowing date, disease severity was lower at Mornag than at Bou Salem. Yield components were measured as number of pods per plant, number of seeds per plant, number of seeds per 100 pods, 100 seed weight and weight of seeds per plant. Both disease severity and yield differed significantly among sowing dates (differently at each location) and also among cultivars for each sowing date, these differences depending both on sowing date and location. A lower yield was always associated with a higher disease severity, although the quantitative relationship differed between cultivars and locations. Cultivar Beja 1 had the lowest vegetative disease scores at both locations and both sowing dates 1 and 2. Beja 1 also scored well for all yield components. Plants sown on the third (latest) date gave the highest yields for all cultivars at both locations (except for an unusually high yield of Neyer at Mornag on sowing date 2), in some instances being more than double those from the earlier sowing dates. Thus, in contrast to other studies, late sowing did not result in yield loss.     

Development of monoclonal antibodies against the fungi of the 'Ascochyta complex'

Two monoclonal antibodies (MAbs) were produced against soluble antigens from the 'Ascochyta complex' fungi. Specificity of MAbs was tested by ELISA using antigen-coated wells. MAbs secreted by the monoclonal hybridoma cell line JIM 44 recognized epitopes present in the antigen preparations from Mycosphaerella pinodes and Phoma medicaginis var. pinodella , but not those present in preparations from Ascochyta pisi . At high tissue culture supernatant concentration, MAbs produced by the monoclonal line JIM 45 recognized epitopes from all three fungi, however, on dilution of MAb the antigens from A. pisi were recognized preferentially to those from M. pinodes and P. medicaginis var. pinodella . On the basis of heat and periodate treatment of the antigens from the three fungi it can be concluded that the epitope recognized by JIM 44 is carbohydrate in nature, whereas that recognized by JIM 45 is proteinaceous in nature, carried on a glycoprotein antigen. Antigen preparations from other fungi, including other pea pathogens, non-pathogens associated with pea and other fungi closely related to the 'Ascochyta complex', were not detected with either of the two MAbs. Antigen preparations from peas could be used to differentiate healthy and infected seeds in a dot-blot assay, therefore indicating the potential of using the MAbs in the development of a diagnostic test for infection of Pisum seeds by the 'Ascochyta complex' fungi.     

Management of bakanae and bacterial seedling blight diseases in nurseries by irradiating rice seeds with atmospheric plasma

The control of seedborne rice seedling diseases in the seed beds is important to avoid epidemics in rice nurseries and paddies, which may result in severe yield loss. Recently, irradiation with plasma containing electrons, creating positive or negative ions and neutral species, has been shown to have an antimicrobial effect, probably via generation of reactive oxygen species. This study examines whether two seedborne rice seedling diseases, bakanae disease caused by the fungal pathogen Fusarium fujikuroi, and bacterial seedling blight caused by Burkholderia plantarii, are suppressed by irradiation of infected rice seeds with atmospheric plasma. Seed germination and seedling growth were not inhibited in plasma‐treated healthy seeds. When F. fujikuroi‐infected rice seeds were irradiated with plasma after being immersed in sterile distilled water, bakanae disease severity index and the percentage of plants with symptoms were reduced to 18.1% and 7.8% of non‐irradiated control, respectively, depending on the duration of plasma irradiation. The bacterial seedling blight disease index was also reduced by plasma irradiation in vacuum‐inoculated seeds to 38.6% of the non‐irradiated control, and in infected seeds harvested from spray‐inoculated heads of rice plants to 40.1% of the control. Therefore, plasma irradiation seems to be effective in controlling two independent seedborne rice seedling diseases.     

我国甘薯新病害-茎腐病的研究初报

 2006年以来广东省主要甘薯产区发现1种甘薯新病害,主要症状表现为叶片变黄,茎基部呈黑色水浸状腐烂,并逐渐沿茎枝向顶端腐烂,后整株倒伏、死亡。从甘薯病茎部分离得到了病菌,经柯赫法则验证为致病病原菌。根据病原菌的形态特征、培养性状、生理生化及16S rDNA序列分析,鉴定其为菊欧文氏菌(Erwinia chrysanthemi)。采用茎枝、菌液共培养法接种8个甘薯品种,结果表明8个品种均无抗病性,病原菌致病性较强。这是我国首次发现该病害。      

First report of Rhizopus stolonifer causing inflorescence and fruit rot of Rauvolfia serpentina in India

Inflorescence and fruit rot caused by Rhizopus stolonifer has appeared for the first time on Rauvolfia serpentina (sarpgandha) in North Indian plains during July–September, 2003. Disease incidence was very high under high humidity and moderate temperature and posing threat to the commercial cultivation of the crop. The initial disease symptoms appear in the form of water-soaked lesions on the flowers and flower buds which later produce slimy wet rot symptoms leading to premature death and drying of infected parts including the leaves. Pathogenicity of R. stolonifer was established artificially under glasshouse conditions.     

Fusarium commune associated with wilt and root rot disease in rice

Wilt and root rot disease in plants has been caused mainly by Fusarium species. Previous studies reported that members of the Fusarium oxysporum species complex (FOSC) were usually associated with this disease, but there has been no report of it being caused in rice by specific Fusarium species. However, in this study, Fusarium commune was identified and characterized as a causal agent of wilt and root rot disease of rice. Four Fusarium isolates (BD005R, BD014R, BD019R, and BD020R) were obtained from different parts (root, stem, and seeds) of diseased rice plants. In morphological studies, these isolates produced key characteristics of F. commune, such as long and slender monophialides, polyphialides, and abundant chlamydospores. In molecular studies, the isolates were identified as F. commune based on sequences of the translation elongation factor 1-α (TEF1) gene that had 99.7%–100% sequence identity with the reference strain F. commune NRRL 28058. The phylogenetic tree showed that all four isolates belonged to the F. commune clade. A mating type test determined that three isolates carried MAT1-2. Their teleomorph stage was still unknown. Pathogenicity assays showed that all the isolates produced wilt and root rot symptoms and the isolate BD019R was observed as the most virulent among the isolates. To our knowledge, this is the first report of F. commune causing wilt and root rot disease on rice.     

Detection and Identification of <Emphasis Type="Italic">Phytophthora</Emphasis> Species in Southern Italy by RFLP and Sequence Analysis of PCR-amplified Nuclear Ribosomal DNA

In four neighbouring regions of southern Italy, Basilicata, Campania, Apulia and Calabria, pepper and zucchini plants showing Phytophthora blight symptoms, tomato plants with either late blight or buckeye rot symptoms, plants of strawberry showing crown rot symptoms and declining clementine trees with root and fruit rot were examined for Phytophthora infections by means of polymerase chain reaction (PCR) assays, using primers directed to nuclear ribosomal DNA (rDNA) repeat sequences. All diseased plants and trees examined tested positive. The detected fungal-like organisms were differentiated and characterized on the basis of primer specificity as well as through extensive restriction fragment length polymorphism (RFLP) and sequence analysis of PCR-amplified rDNA. Phytophthora capsici was identified in diseased pepper and zucchini plants, P. infestans was identified in tomato with late blight symptoms whereas buckeye rot-affected tomatoes and diseased strawberry plants proved to be infected by P. nicotianae and P. cactorum, respectively. Declining clementine trees were infected with P. citrophthora and P. nicotianae in about the same proportion. Also, thirty-one pure culture-maintained isolates of Phytophthora which had previously been identified in southern Italy by traditional methods but were never examined molecularly, were examined by RFLP and sequence analysis of PCR-amplified nuclear rDNA. Among these, an isolate from gerbera which had previously been identified by traditional methods only at genus level, was assigned to P. tentaculata. For the remaining pure culture-maintained isolates examined, the molecular identification data obtained corresponded with those delineated by traditional methods. Most of the diseases examined were already known to occur in southern Italy but the pathogens were molecularly detected and fully characterized at nuclear rDNA repeat level only from other geographic areas, very often outside Italy. A new disease to southern Italy was the Phytophthora blight of zucchini. This is also the first report on the presence and molecular identification of P. tentaculata from Italy.     

Resistance in field pea (Pisum sativum) to the black spot disease complex in Western Australia

Black spot (also referred as Ascochyta blight, Ascochyta foot rot and black stem; Ascochyta leaf and pod spot) is a devastating disease of field pea (Pisum sativum) caused by one or more pathogenic fungi including Didymella pinodes, Ascochyta pisi, Phoma pinodella and P. koolunga. Development of resistant germplasm has been slow because of the low level of resistance found in the available germplasm, poor reliability of screening methods and the polygenic nature of inheritance. Field studies, undertaken to assess F8 and F9 derived lines for resistance against the black spot complex, confirmed that some lines developed in the Australian breeding program show improvement in resistance over commercial cultivars. Disease scores across test lines ranged from 5.33 to 7.82 (0–9 scale where 0?=?no disease symptoms, and 9?≥?90 % leaf area affected) and from 5.37 to 8 in 2012 and 2013, respectively. In 2012, the eight most resistant lines had scores 5.33 to 6, with OZP1207 the most resistant line. In 2012, forty three lines were significantly more resistant (disease score?≤?6.67) than the susceptible standard, Helena (7.82), 14 lines were not significantly different to the most resistant commercial cultivar, Parafield (6.33), and 27 lines were significantly more resistant than PBA Percy (7.67). In 2013, WAPEA2211 was clearly the most resistant line (5.37) followed by a group of seven lines with slightly less resistance scored at 6. Use of these lines in breeding will further enhance resistance in commercial cultivars, particularly by inter-crossing among the more genetically diverse lines to accumulate minor genes for resistance. While there was no overall relationship between disease scores in 2012 and 2013 (R ²?=?0.029), presumably due to the highly variable pathogen composition of the black spot complex at the screening site and across seasons in Western Australia, a few lines, such as WAPEA2211, 04H349P-05HO2005, 06H109P-9 and 06H459P-1, showed significant resistance in both years, appear to have resistance to multiple pathogens in the black spot complex, and are of particular significance.     

一种值得关注的花生新病害：花生新赤壳菌基腐病

2010年在我国广东省首次报道了由侵管新赤壳菌(Neocosmospora vasinfecta)侵染引起的花生新赤壳菌基腐病.罹病花生植株萎蔫、植株茎基部和根系变黑腐烂,在潮湿条件下,罹病部位有浅红色子囊果.这是我国大陆首次报道的花生新病害.该病害在广东省的多个市县有发生,严重的发病率高达30％.除广东省外,该病在我国江西省也有分布和危害,其致病菌可进一步鉴定为侵管新赤壳菌非洲变种(N.vasinfecta var.africana).在广东省也发现了由侵管新赤壳菌侵管变种(N.vasinfecta var.vasinfecta)引起的大豆茎枯病.对侵管新赤壳菌的文献进行了简要的综述.     

Ascochyta blight of chickpea in Australia: identification, pathogenicity and mating type

The aetiology of blight of chickpea in South Australia was studied following sporadic disease outbreaks over several years that had been tentatively identified as Phoma blight. Nine fungal isolates from diseased chickpeas were tested for pathogenicity in the glasshouse, of which two caused symptoms resembling those of Ascochyta blight. The two aggressive isolates were identified as Ascochyta rabiei based on morphological characteristics of cultures and RAPD analysis. This was further confirmed by successful mating to international standard isolates, which showed that the two Australian isolates were MAT1-1. These isolates are accessioned as DAR 71767 and DAR 71768, New South Wales Agriculture, Australia. This is the first time that A. rabiei has been positively identified in commercial chickpeas in the southern hemisphere. The pathogen was found (in 1992) in only one of 59 seed samples harvested throughout Australia between 1992 and 1996 and tested using International Seed Testing Association methods. The teleomorph has not been found in Australia and results to date suggest that only one mating type is present. This suggests that quarantine restrictions on imported chickpea seed should be retained to prevent the introduction of the opposite mating type.     

The occurrence in Portugal of the bacterial disease of maize crops caused by Erwinia chrysanthemi

A bacterial disease causing stalk rot of maize was observed in Portugal, during the summer of 1991, in overhead sprinkler-irrigated fields. Affected plants showed symptoms of a soft rot disease and isolations made from infected tissues consistently yielded a bacterium. On the basis of morphological, cultural, biochemical, physiological and pathological properties, the pathogen was identified as Erwinia chrysanthemi. According to biovar discrimination tests, the maize isolates were allocated to biovars 2 and 3 of E. chrysanthemi.     

Seed treatment prevents vertical transmission of<Emphasis Type="Italic">Fusarium moniliforme</Emphasis>, making a significant contribution to disease control

Fusarium moniliforme is a widespread facultative endophyte, primarily associated with corn, where it causes extensive crop damage.F. moniliforme can be toxigenic, the carcinogenic fumonisins being accumulated predominantly when the fungus colonizes corn plants. The pathogen is transmitted both through contaminated seeds and through environmental inoculum. This study utilized markednit-mutantF. moniliforme inoculum in order to evaluate the quantitative significance of seedborne disease transmission. Greenhouse and field trials demonstrated that seedborne isolates were responsible for up to 50% ofF. moniliforme disease. Seed treatment with the fungicide prochloraz was found to control seedborne transmission and to protect againstF. moniliforme seedling blight. The elimination of seedborne inoculum resulted in reduced incidence of kernel rot and avoided the increment in soil inoculum accumulation associated with the introduction of infected seeds. http://www.phytoparasitica.org posting July 10, 2003.     

云南省宝株梨上发生的梨疫腐病

宝株梨疫腐病是我省会泽县近年来发生的1种新病害,其病原菌为霜霉目疫霉科的恶疫霉Phytopthora　cactorum（Lebertet Cohn）Schrot.本文对该病的发病情况、病害症状、病菌来源及防治等进行了初步研究。